Phosphoinositide-3-kinases (PI3Ks) are a group of lipid kinases, which phosphorylate the 3-hydroxyl of phosphoinositides. They are classified into at least three classes (classes I, II, and III) and play an important role in cellular signaling (Stephens et al., Curr. Opin. Pharmacol. 2005, 5, 357). Class I enzymes are further classified into classes Ia and Ib based on their mechanism of activation. Class Ia PI3Ks are heterodimeric structures consisting of a catalytic subunit (p110α, p110β, or p110δ) in complex with a regulatory p85 subunit, while class-Ib PI3K (p110γ) is structurally similar but lacks the p85 regulatory subunit, and instead is activated by βγ subunits of heterotrimeric G-proteins (Walker et al., Mol. Cell. 2000, 6, 909).
PI3Ks play a variety of roles in normal tissue physiology (Foukas & Shepherd, Biochem. Soc. Trans. 2004, 32, 330; Shepherd, Acta Physiol. Scand. 2005, 183, 3), with p110α having a specific role in cancer growth, p110β in thrombus formation mediated by integrin αIIβ3 (Jackson et al., Nat. Med. 2005, 11, 507), and p110γ in inflammation, rheumatoid arthritis, and other chronic inflammation states (Barber et al., Nat. Med. 2005, 11, 933; Camps et al., Nat. Med. 2005, 11, 936; Rommel et al., Nat. Rev. 2007, 7, 191; and Ito, et al., J. Pharm. Exp. Therap. 2007, 321, 1). Therefore, there is a need for PI3K inhibitors for treating cancer and/or inflammatory diseases.